Constantine was the son and successor of Emperor Leo III and Maria. His derogatory nickname Kopronymos derives from kopra (feces ) and onoma (name ). The nickname used by the hostile iconodule sources refers to him allegedly defecating in the baptismal font or the imperial purple cloth with which he was swaddled.
In August 720 he was associated on the throne by his father, who had him marry Tzitzak , daughter of the Khazar khagan Bihar . His new bride was baptized as Irene (Eir, "peace") in 732. Constantine V succeeded his father as sole emperor on April 19 , 741 . The accession of the new emperor went as smoothly as expected, but his authority was soon to be challenged.
Civil war against Artabasdos
Constantine was crossing Asia Minor to campaign against the Umayyad Caliphate under Hisham ibn Abd al-Malik on the eastern frontier in June 741 or 742. But during this course Constantine was attacked by the forces of his brother-in-law Artabasdos , the strategos of the Armeniac theme . Defeated, Constantine sought refuge in Amorion , while the victor advanced on Constantinople and was accepted as emperor. While Constantine now received the support of the Anatolic and Thracesian themes, Artabasdos secured that of the themes of Thrace and Opsikion, in addition to his own Armeniac soldiers.
After the rival emperors had bided their time in military preparations, Artabasdos marched against Constantine, but was defeated in May 743. Three months later Constantine defeated Artabasdos' son Niketas and headed for Constantinople. In early November Constantine was admitted into the capital and immediately turned on his opponents, having them blinded or executed. Perhaps because Artabasdos' usurpation was interconnected with the restoration of image worship, Constantine now became an even more fervent iconoclast than his father.

In February 754 Constantine convened a synod at Hieria, which was attended entirely by Iconoclast bishops. The council approved of Constantine's religious policy and secured the election of a new Iconoclast patriarch. It was followed by a campaign to remove images from the walls of churches and to purge the court and bureaucracy from Iconodules .
Since monasteries tended to be strongholds of Iconophile sentiment, Constantine specifically targeted the monks, pairing them off and forcing them to marry nuns in the Hippodrome and expropriating monastic property for the benefit of the state or the army. The repressions against the monks (culminating in 766) were largely led by the emperor's general Michael Lachanodrakon, who threatened resilient monks with blinding and exile.
An iconodule abbot, Stephen Neos, was brutally lynched by a mob at the behest of the authorities. As a result many monks fled to Southern Italy and Sicily . By the end of Constantine's reign, Iconoclasm had gone as far as to brand relics and prayers to the saints as heretical .
Constantine was an able general and administrator. He reorganized the themes , the military districts of the empire, and created new field army divisions called tagmata . This organization was intended to minimize the threat of conspiracies and to enhance the defensive capabilities of the Empire. With this reorganized army he embarked on campaigns on the three major frontiers.

In 746, profiting by the unstable conditions in the Umayyad Caliphate which was falling apart under Marwan II , Constantine invaded Syria and captured Germanikeia (Maras , his father's birthplace). He organized the resettlement of a part the local Christian population into imperial territory in Thrace . In 747 his fleet destroyed the Arab fleet off of Cyprus .
In 752 Constantine led an invasion into the new Abbasid Caliphate under As-Saffah . Constantine captured Theodosioupolis and Melitene (Malatya ), and again resettled some of the population in the Balkans . These campaign failed to secure any concrete gains (apart from additional population employed to strengthen another frontier), but it is important to note that under Constantine V the Empire had gone on the offensive.
These successes made it possible to pursue an aggressive policy in the Balkans. With the resettlement of Christian populations from the East into Thrace, Constantine V aimed to enhance the prosperity and defense of this area. This caused concern to the Empire's northern neighbor, Bulgaria , and the two states clashed in 754. Kormisosh of Bulgaria raided as far as the Anastasian Wall , but was defeated in battle by Constantine V, who inaugurated a long series of successful campaigns against the Bulgarians. Constantine's victories, including that at the Anchialus in 763 caused considerable instablity in Bulgaria, where six monarchs lost their crowns on account of their failures.
This lucky streak ran out in 775, when Constantine was persuaded to reveal to the Bulgarian ruler Telerig the identities of his agents in Bulgaria. These were promptly eliminated, and Constantine began preparions for a new campaign against the Bulgarians, during the course of which he died on September 14 , 775 .
Iconophiles considered his death a divine punishment. They spread the rumour that he had defecated in his baptismal font as a baby, and began to refer to him as Kopronymos. In the 9th century he was disinterred and his remains were thrown into the sea

742-743 AD
The Byzantines declared war on the Arabs, but soon after this, a civil war broke out in the Byzantine Empire which halted the entire affair. Leading the opposing faction was Strategus Artabasdus from the Armeniakon Theme who already was married to Constantine's sister. General Artabasdus attacked the Emperor's forces in the Ospikion Theme (Asia Minor) and defeated them. The Emperor was forced to flee Constantinople, but later defeated Artabasdus at Sardes in 743
757 AD
Emperor Constantine V landed at the mouth of the Danube with his Byzantine legions and ravaged the Bulgar territory around it. After a time, the Emperor took his forces and marched south to the Fortress of Marcellae where he defeated the Bulgar army who was trying to siege it. The loss was so complete for the Bulgars, that the Slavs began thinking about their own independence.
758 AD
The Byzantines attacked and subdued the Slavs in Thrace and Macedonia under Emperor Constantine V who were wanted to set up their own independent state free of Bulgars and Byzantines. The Khazars and the Arabs arranged better relations between each other by a diplomatic marriage of a Khazar princess to the Caliph, al-Mansur (754-775 AD).
759 AD
The Bulgars were defeated by the Byzantine legions at the Battle of Vergava (between Pliska and Diampolis). Emperor Constantine V then had a large Byzantine occupational force set itself up in the midst of the Bulgarian Khanate near Vergava. Later on, Kana Subigi Vinekh attacked and destroyed the occupational force which included the death of a Thracian Strategus. However, the previous defeats directly under the Emperor caused the Bulgar leader to sue for peace rather than suffer another possible defeat (the Khanate's one victory was when the Emperor was away). According to Vernadsky, a mixture of Slavs and Bulgars attacked the Byzantine occupational force, but did not get further because of internal conflicts between the two peoples.
The Khazar princess died in supposed childbirth, so the Khazars who were suspicious of the incident declared another war upon the Arabs. The Sabiri who numbered 10,000 warriors rode with their commander in the Khazar military called an, As-Tarkhan, against the Arabs and slew many past the Caucasian Gates in the Arabic territories. Additionally noted, the Arab Northern Army was defeated by the Khazars, with the Sabiri taking control of an area called, al-Laks
763 AD
Emperor Constantine V decided to attack the Bulgarian Khanate by using his navy to carry cavalry up to mouth of the Danube River as well as making a major thrust up north into Thrace as a second manuever (which was done with the bulk of his legions). His cavalry attack ravaged the economy behind enemy lines once in position, and then rode through Dobrudja to meet the Emperor before the battle was joined with Kana Subigi Teletz at the frontier. Kana Subigi Teletz sensing this, decided to attack the Emperor as quickly as possible while his forces were camped at Anchialus along the Gulf of Burgas. On June 30th, the Hunno-Bulgars engaged the Byzantines at the Battle of Anchialus. The battle raged and casualties were high on both sides, but the day was won by the Byzantines. No chase was given by the Byzantines because of their losses being too extreme, so the Emperor returned to Constantinople.
773 AD
Sensing the growing power of the Hunno-Bulgars, Emperor Constantine V set forth by land and by sea to either destroy the Bulgars or put them into servitude through another of his peace treaties. Accordingly, in May of this year, 2,000 transports carried cavalry as well as the Emperor to the mouth of the Danube River, while his legions marched through Thrace. After fierce fighting the Bulgars were not able to stop the advance of the Northern Byzantine Army which descended towards the city of Varna, so Kana Subigi Telerig sued for peace (which the Byzantines granted) before things got worse for his people.
Kana Subigi Telerig convinced House Ugain and the anti-Byzantine faction that he had no intention of upholding the terms of the treaty. While he sent his diplomatic Tabar Tsigat to discuss the terms of the said 'peace', he gathered 12,000 cavalry to invade Thessaly. This was mainly done to round up the local population there and deport them back into the Khanate (the population in Thessaly mainly consisted of Berzetian Slavs). By October while the terms of the peace treaty were still being discussed in Constantinople, the Emperor became informed of the gathering of these forces to invade Thessaly through his network of spies. Immediately, he assembled his own army in front of Tabar Tsigat saying that they were going fight a new campaign against the Arabs. The deception was believed, and an army of 80,000 Byzantine troops was dispatched to intercept the Hunno-Bulgar force. When the forces met each other in the Balkan Mountains along the River Sliven, the Bulgars merely turned around and left the Byzantine territory on account of the one to eight odds using the speed of their horses to leave the Byzantines behind. No pursuit by the imperial forces was given and they even called it the 'Noble War' since no one was killed, but this was just good old Byzantine propaganda.
774 AD
Byzantine Emperor Constantine V planned another of his infamous two spearhead attacks, one by by land through Thrace, and the other to attack Varna by sea. However, the naval defenses at Varna setup under the reign of Kana Subigi Tervel thwarted the landing which then had to turn out to sea where it met with disaster by fierce weather. The Emperor then called off his campaign.
Kana Subigi Telerig realized that the Byzantine spy network at home had to be dealt with, so he cunningly sent a message to the Emperor that he was in danger from a rival political faction with the Khanate. Furthermore, he stated that he would need a list of the agents in Bulgaria to retreat to, should things get out of hand.
The Emperor Constantine V concurred and sent him the list which Kana Subigi Telerig used promptly in executing all the traitors in his midst.
775 AD
Emperor Constantine V, outwitted by the Bulgars and furious at Kana Subigi Telerig's cunning, attacked the Bulgarian Khanate again in September. However, he became sick with a fever early in the campaign and died at the Fortress of Strongylus on September 14th, 775 AD. No doubt it was a good day for the Hunno-Bulgars since he was personally responsible for wrecking their economy, military, and morale amongst it's people on many occasions. In a sense at his death, the spirit of the Bulgar heart was one which hated the Byzantines and had galvanized the Bulgarian Khanate to despise their wealthy neighbors over Constantine V's nine military campaigns.